Q. Monochromatic light of frequency $5 \times 10^{14}\ $Hz travelling in vaccum enters a medium of refractive index 1.5. It wavelength in the medium is
A) $4000\mathring{\mathrm{A}}$
B) $5000\mathring{\mathrm{A}}$
C) $6000\mathring{\mathrm{A}}$
D) $5500\mathring{\mathrm{A}}$
Explanation
(a) Wavelength in vacuum,
$\lambda = \frac{3 \times 10^{8}}{5 \times 10^{14}} \times 10^{10}\mathring{\mathrm{A}} = 0.6 \times 10^{4}\mathring{\mathrm{A}}$
$= 6000\mathring{\mathrm{A}}$
Now,$\ \ \mu = \frac{\lambda}{\lambda^{'}}$
Or $\ \lambda^{'} = \frac{\lambda}{\mu} = \frac{6000}{1.5}\mathring{\mathrm{A}} = 4000\ \mathring{\mathrm{A}}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.